1. Field of the Invention
The present invention generally relates to cascode devices, and more specifically to biasing cascode devices without an external biasing circuit.
2. Background Art
Communications circuits often include a differential configuration and differential amplifier to improve noise performance. Using a cascode configuration in a differential pair is a common practice. The advantages include, but not limited to, providing more isolation from the input to the output of the trans-conductor stage, higher impedance at the output of the input trans-conductor thereby boosting the gain, and protecting the drain of the input devices. As a result, the cascode configuration is quite popular in differential pairs. However, the cascode devices require a bias voltage. This is usually done by adding some circuitry particularly for this purpose which is undesirable for very low-power applications.
Therefore, what is needed is a cascode configuration in a differential amplifier with a low power bias circuit configuration.